At present, a discharge type fluorescent lamp and an incandescent bulb used as the illumination device involve problems that a harmful substance such as mercury is contained, and life span is short. However, in recent years, a high luminescence LED emitting light of blue to near ultraviolet/ultraviolet region has been developed in sequence, and a study and a development have been actively performed, on creating white light by mixing near ultraviolet/ultraviolet to blue light emitted from the LED and the light emitted from the phosphor having an excitation band in a wavelength region thereof, and using such a white light as an illumination of the next generation. When the white LED illumination is put to practical use, there are advantages such as being highly efficient in converting an electrical energy into light with less heat generation, having a good life span without burn-out of a filament as is seen in a conventional incandescent bulb because it is constituted of the LED and a phosphor, including no harmful substance such as mercury, and realizing a small size illumination device. This contributes to obtaining an ideal illumination device.
In the same way as the light emitting device such as a usual fluorescent lamp, the light emitting device comprising the LED and the phosphor, with low power consumption and high luminance and having improved efficiency is desired. In order to improve the efficiency of a device itself, in addition to improvement in extraction efficiency of light from a semiconductor device which is an excitation source, the phosphor capable of efficiently converting the light becoming the excitation source into a different wavelength is desired. Particularly, the phosphor capable of efficiently emitting light in the near ultraviolet/ultraviolet to blue region, which is an emission wavelength of the semiconductor device, is desired.
Therefore, the study on the phosphor with excellent efficiency is actively performed at present, along with a further improvement in the conventional oxide base, sulfide base, and phosphoric phosphors, in recent years, the phosphor with new composition like a nitride phosphor such as Ca2Si5N8:Eu, Sr2Si5N8:Eu, Ba2Si5N8:Eu, CaSrSi5N8:Eu, and Sr2Si5N8:Ce, (see patent documents 1 and 2), and an oxynitride phosphor such as Sr2Si3Al2N8O2:Eu (see patent document 3) have been developed in a sequence. Some of the phosphors containing nitrogen are excellent in temperature characteristic and durability, thereby having been used in the light emitting device such as a white LED lighting unit.    (Patent document 1) Japanese Unexamined Patent Publication No. 2003-515655    (Patent document 2) Japanese Patent Laid Open No. 2004-244560    (Patent document 3) International Publication No. 2004/055910 A1 Pamphlet
The phosphor thus containing nitrogen has an excellent emission efficiency and has an excellent durability to heat and water. However, the phosphor thus containing nitrogen according to the conventional art does not have an emission efficiency with satisfactory level under an excitation of an excitation light from the near ultraviolet/ultraviolet to green regions, thereby not having a sufficient emission intensity and luminance. Therefore, although the white LED lighting unit having the excellent durability can be manufactured, the luminance, which is an important element, becomes insufficient when the light emitting device is manufactured by combining the near ultraviolet/ultraviolet LED, blue LED, etc., and the phosphor thus containing nitrogen, because the emission intensity and the luminance are insufficient. Further, as a manufacturing method of the phosphor thus containing nitrogen according to the conventional art, there is no choice but use a nitride raw material which is unstable in an atmospheric air, because the emission efficiency is decreased when a slight amount of oxygen is included during mixing the raw materials. Also, there is no choice but use the method of treating and mixing the raw materials in the inert atmosphere to prevent the oxidization of the nitride raw material during mixing the raw materials, or fire the raw materials in a strong reducing atmosphere and a nitride atmosphere such as 100% ammonia. Therefore, it is difficult to improve the productivity.